In the prior art, organopolysiloxane compositions are widely used in a variety of applications because of their heat resistance, freeze resistance, and electrical insulation. Most of such organopolysiloxane compositions make use of the addition reaction between an organopolysiloxane having an alkenyl radical attached to a silicon atom and an organohydrogenpolysiloxane having a hydrogen atom attached to a silicon atom. Organopolysiloxane compositions of the addition reaction type are generally used for the purpose of rendering tack-free the surface of substrates like films, sheets, and non-woven fabrics of celluloses, synthetic resins, and synthetic fibers.
However, a heat treatment at 130.degree. to 150.degree. C. for about 30 to 60 seconds was generally necessary to convert an organopolysiloxane composition of the addition reaction type applied to the substrate into a cured coating having release properties. In order to impart release properties to less heat resistant substrates such as paper and synthetic resin films like polyethylene, polypropylene and polyvinyl chloride by forming a cured coating of organopolysiloxane thereon, it was essential to mitigate high temperature/long term heating conditions. There was a need for a silicone composition which can be readily cured into a coating at relatively low temperatures within a relatively short time. It was proposed to add relatively large amounts of platinum base catalyst to an organopolysiloxane composition of the addition reaction type in order to form a cured coating at relatively low temperatures within a relatively short time. However, this approach suffers from problems that it is uneconomical, the composition has poor shelf stability or a short pot life, and the resulting cured coatings show inconsistent release performance.
Attempts were made to solve the problems associated with large amounts of platinum base catalysts added to organopolysiloxane compositions of the addition reaction type, typically by using addition reaction controlling agents, for example, carbon tetrachloride (Japanese Patent Publication No. 6111/1972), acetylene alcohols (Japanese Patent Publication No. 31476/1969), acrylonitrile (Japanese Patent Publication No. 22018/1970), 1,3-dichloropropene (Japanese Patent Application Kokai No. 238851/1986), and maleates (U.S. Pat. Nos. 4,256,807, 4,530,989, and 4,562,096). However, the use of CCl.sub.4 as the addition reaction controlling agent has a problem that no significant control of addition reaction could be accomplished unless CCl.sub.4 is used in large amounts. Since the acetylene alcohols are reactive with hydrogen-silicon bonds, the hydrogen silicon bonds which are curing functional groups in the composition are consumed with time so that the composition loses its curing ability. In addition, since acetylene alcohols are volatile and have low flash points, they can be added only in limited amounts to organopolysiloxane compositions in the form of solventless coating liquid in view of safety. Since the acrylonitrile is weak in controlling the addition reaction, it must be added in large amounts in order to provide an effective control. Organopolysiloxane compositions containing large amounts of acrylonitrile suffer from a problem of short-curing and an environmental problem because the acrylonitrile gives off an offensive odor.
Other addition reaction controlling agents were proposed, for example, diallyl maleates, maleimides, and hydrocarboxymaleates. However, all these compounds are less soluble in organopolysiloxanes, and thus added only in limited amounts in order that the organopolysiloxane compositions can uniformly cure into a thin coating. They are thus still unsatisfactory.